The present invention relates to a bamboo floor plate featuring improved sound insulation in addition to thermal insulation and heating effects.
Sounds are generated from innumerable sources including speech, human behavior and various utensils. These sounds do not cause much of a problem in detached houses, but in multi-storied apartment houses, these sounds are transmitted through walls, ceilings and floors from one apartment to another because the apartments are adjacent to one another vertically and horizontally. Therefore, it has become commonplace to make the walls, ceilings and floors substantially thick as well as using vibration insulation and sound insulation materials.
In multi-storied apartment houses, thick ceilings, floors and walls thick are effective in insulating sound, but the use of thick components inevitably increases the volume of concrete used, and pushes up the building cost. On the other hand, to obtain the same sound insulating effect using an alternative material can result in a complicated structure, which also increases the building cost. As such, an aesthetic and low-cost building material having a sound insulating effect, strength and polish has been desired, but such a material has not been materialized so far.
Bamboo materials are easy to reproduce. Thanks to the advances in production devices, it is now possible to flatten a round bamboo cane or make laminated bamboo materials of enlarged sizes at low cost. The value of bamboo as a building material has increased, and its use as an alternative material for some applications that were exclusively achieved by wood in the past has recently been studied. A bamboo plate is characterized by a surface grain made by straight fibers, which provides it with hardness and high flexural strength. On the other hand, a bamboo plate is not very effective in insulating sound. As a flooring material, a bamboo plate barely achieves Class 2 of the lightweight floor impact value LL of JIS (Japanese Industrial Standard).
The objective of the present invention is to provide a bamboo floor plate for sound insulation that is used as a building material, featuring the bamboo""s aesthetic appearance and strength as well as improved sound insulation, thermal insulation and a heating capability.
The present invention is a bamboo floor plate for sound insulation comprising a bamboo plate made by developing a round bamboo cane flat or by cutting it into pieces and laminating them till they make a plate of an adequate size, characterized in that several grooves are formed on the bamboo plate, and a non-bamboo plate is pasted on the surface on which the grooves are provided, and several hollows are formed between the bamboo plate and the non-bamboo plate.
In this invention, a bamboo cane is developed flat and laminated with glue into an adequate size bamboo plate for use as a building material. On one surface of the bamboo plate, several grooves are provided at adequate intervals to form hollows that prevent transmission of sounds as well as to eliminate the causes for warping. On the surface on which the grooves are provided, a non-bamboo plate is glued to make a compound bamboo plate with hollows, thereby improving the sound insulation and thermal insulation effects. The many grooves are effective in softening the hardness of the surface on which the grooves are provided.
The bamboo plate equipped with such effects retains the bamboo""s original aesthetic appearance. In a simplified test for floor impact sounds on a concrete floor using a 15 to 16 mm thick compound bamboo plate (i.e. combination of the above bamboo plate and a foam plastic sheet), the lightweight floor impact value LL of the JIS was approximately 30 dB at an octave range middle frequency of 500 Hz. This translates into an improvement of approximately 40 dB in the floor impact sound compared with a simple concrete floor. This sound insulation value corresponds to L-40 of the sound insulation classification.
When a combination of the above bamboo plate with a non-woven fabric is directly spread on a concrete floor, the lightweight impact value LL was 41 dB at 500 Hz and 34 dB at 1000 Hz, translating into floor impact sound level improvements of 32 and 39 dB respectively, indicating that its frequency characteristic was different from the one combined with the foam plastics heet. When the above compound bamboo plate was installed on the joists filled with glass wool on a concrete floor, similar results were obtained.
The hollows formed in the bamboo plate for sound insulation is also effective in increasing thermal insulation in addition to sound insulation, and is useful in softening the hardness of the bamboo plate as well as preventing its warping. When the bamboo plate for sound insulation is glued on a concrete floor, which has low smoothness, the addition of a non-bamboo material to the bamboo plate for sound insulation improves the adhesion to the other material, simplifying and speeding up the construction.
The plate to cover the surface on which the grooves are provided is made by combining various materials selected from foam materials made of thermoplastic or thermosetting plastic or rubber, or from non-woven sheets, using glue. The material made as such has adequate elasticity on its surface so that even if there is some roughness on the surface of the other part, such roughness is easily absorbed. As a result, the flatness of the floor surface is maintained. Such a plate, therefore, makes an excellent building material providing both sound insulation and thermal insulation. It is also possible to insert a hard material such as lumber in between the surface on which the grooves are provided and the above-mentioned materials.
To make a heating plate that forms a building material equipped with a heating capability, a sheet-shaped heating plate equipped with an electrode of an adequate shape sandwiched by insulation materials can be inserted in between the bamboo plate and the non-bamboo plate. Or, conductive resin made by mixing conductive carbon powder (e.g. carbide) into a plastic material in a weight ratio of 30 to 60% can be embedded in the groove with an electrode, the inside of which is insulated. In this structure, it is preferable that a material with a high thermal insulation capability be used for the non-bamboo plate.
To make the thickness of the bamboo floor plate for sound insulation within the range of 10 to 25 mm, the thickness of the bamboo plate itself or the laminated plate of the bamboo plate and plywood should be within the range of 5 to 15 mm. The thickness of the plate combined with a non-bamboo plate should be: 0.5 to 15 mm if the non-bamboo plate is a foam sheet made of a rubber or plastic material; 3 to 15 mm if the non-bamboo plate is a non-woven fabric; and 1 to 5 mm if the non-bamboo plate is a sheet-shaped heating plate. The cross section of the groove should be rectangular or trapezoid. The arrangement of the grooves should be selected from parallel, perpendicular or crossed with respect to the fiber of the bamboo.
The depth of each groove is selected from within the range of 10 to 70%, preferably 20 to 60% of the thickness of the bamboo plate itself or the laminated plate made of the bamboo plate and plywood. The width of each groove is selected from within the range of 1 to 10 mm, preferably 1 to 5 mm. The interval between the grooves is selected from within the range of two to twenty times, preferably eight to fifteen times that of the width of each groove. The size of the groove should be large for the purpose of filling heating materials within for heating, and small for the purpose of sound insulation. The flooring material may be a square-shaped panel, but a rectangular material combining a width of 70 to 160 mm and a length of 700 to 2000 mm costs less and is easier to use.
Usually the grooves are formed by cutting into the bamboo plate. However, that requires a thick bamboo plate, which pushes up the production cost. To avoid this, it is possible to make the grooves from a combination of a primary material and a plurality of secondary materials, which are combined by an adhesive. The primary and secondary materials are each made from a thin bamboo plate itself or the laminated plate made of a thin bamboo plate and plywood. The secondary material may be of the same length as the width of the primary material and has the width range of 10 to 50 mm, preferably 15 to 40 mm. The thickness of the secondary materials is the same as the depth in the preceding paragraph. The space between each secondary materials is also the same as in the preceding paragraph.